1. Field of the Invention
The present invention relates to the destruction and recycling of asbestos wastes and, more particularly, to an apparatus and system for the process of mineralogical conversion of asbestos waste to accelerate or otherwise improve the efficiency of the mineralogical conversion process that is employed for conversion of asbestos waste into non-asbestos products.
2. Description of the Related Art
Asbestos is a term referring to a family of historically useful fibrous minerals that most commonly belong to the serpentine and amphibole mineral groups including such species as chrysotile, crocidolite, amosite, and anthophyllite. More precisely referred to as “asbestiform minerals”, they are hydrated silicates that generally contain substituted iron, calcium, magnesium, and sodium in various proportions. The Serpentine group of minerals including chrysotile, antigorite and lizardite are all represented by the approximate composition: Mg3[Si2O5] (OH)4. Of these, chrysotile represents the majority of all asbestos minerals consumed for industrial and commercial purposes. There is substantial variation in mineral chemistry and physical characteristics of asbestiform minerals but they all have similarities in basic structure that is typically modified because of variations in the concentrations of calcium, iron, magnesium and sodium.
Asbestos has been used in thousands of products and in numerous workplaces. Although the harm caused by asbestos is not apparent at first, asbestos exposure can lead to serious, debilitating, and often fatal diseases. These include mesothelioma, asbestos lung cancer, and asbestosis. Usually, a period of 10 to 40 years or more passes before the asbestos victim exhibits the first asbestos disease symptoms. In the workplace, there is no “safe” level of asbestos exposure. For this reason, increased limitations and restrictions on its use in commercial products, handling and disposal have been and continue to be imposed in many countries around the World.
As a toxic mineral, various attempts have been made to render asbestos inert. Attempts to destroy asbestos waste using heat alone to alter asbestos fiber chemistry have met with only limited success since asbestos fibers by their very nature are refractory and self-insulating. For example, chrysotile fibers have been reported to withstand temperatures up to 3000° F. for time periods of up to one-half hour. Since such a technique requires very high temperatures for fiber destruction, this approach has proved quite uneconomical.
Several vitrification (or melting) processes such as plasma melting and joule heating have shown success in destroying asbestiform minerals. However, these processes are energy intensive and require very expensive and complex equipment. Thus, vitrification processes, although capable of destroying asbestos waste have not exhibited commercial viability.
Other methods utilizing reduced process temperatures and a variety of chemical additives have also been attempted. With one exception, they have also met with limited success. The process “Mineralogical Conversion of Asbestos Waste” described in U.S. Pat. No. 5,096,692, which is incorporated in its entirety herein by reference, is the one sub-melting point process that has achieved commercial development. In that patent, asbestos waste is converted to non-asbestos products below the melting point by the combination of chemical additives and application of heat.
During the commercial development of Mineralogical Conversion of Asbestos Waste, it was found that the time required to convert 100% of the asbestos fibers in the waste took longer than that which would be required for highly competitive processing. Processing times of up to 60 minutes were required to assure that all of the asbestos fibers in the waste experienced destruction. It is desirable to reduce the processing time in order to enhance the feasibility of this process for large scale commercial applications.